It is recognized in the art that a variety of factors must be considered when designing cooling systems for electronic equipment such as a large scale computer system. These concerns include the performance of the system, cost, reliability and the amount of maintenance required for the system.
As has been stated in U.S. Pat. No. 4,674,004 entitled "Parallel-Flow Air System for Cooling Electronic Equipment", a system characterized by simplicity yet still providing adequate cooling for the electronic equipment represents the best solution to a thermal cooling problem. Air cooling is generally regarded in the art as the most simple and reliable such system. However, as recognized in the above mentioned patent, the power density on computer cards continually increases and it becomes increasingly more difficult to cool with air.
Better cooling schemes typically involve blowing air across the computer card in a direction parallel to the surface of the card. As the air travels across the card it picks up heat in a serial fashion from the components mounted thereon and the air increases in temperature. With the rise in card power levels, large bodies of air are needed to keep the air temperature rise from exceeding acceptable levels.
The cooling problem is further exacerbated by the increase in power and size of the integrated circuit packages for components mounted thereon. The high power levels of these devices result in higher than average local temperature rises. Each pocket of high temperature air is directed by the air flow onto the next package in a system such as that mentioned above. Also, as such devices become physically larger the device tends to block the flow of air to the downstream packages in the system.
Because of each of these mentioned thermal effects, packages at the end of the air stream in such an environment face a flow of high temperature, low velocity air. In addition, the thermal effects of such systems become more difficult to control in proportion to the increase in physical size and power dissipation of the circuit boards and circuit packages mounted thereon.
U.S. Pat. No. 4,674,004 teaches a system in which a parallel air flow system provides a series of card-duct assemblies within the foreplane area of a computer system in which the circuit boards mentioned above are located to provide a directed air flow to each of the components dispersed on the circuit boards therein.
Recent advances in system design have created a new problem for cooling such electronic equipment. The environment for which the present invention is well-suited to provide cooling is one in which electrical components are mounted on the opposite side of a backplane from that on which the cooling air is dispersed.
Mounting components on this backplane side of a backplane creates a series of environmental constraints making it particularly difficult to deliver cool air to the location. In particular, there is a limited space in which to implement a cooling system without expanding the cabinet of the system itself, which is not desirable. In such a constrained environment there is such limited space that the use of an additional air handler and/or adequately sized heat sinks is not practical. Such solutions would cause an increase in the size of the system cabinet. They also increase the cost of the system to add the additional air handler and/or heat sinks.